package com.study.filter;

import com.alibaba.fastjson.JSON;
import com.study.constant.CommonConstant;
import com.study.constant.GatewayConstant;
import com.study.util.TokenParseUtil;
import com.study.vo.JwtToken;
import com.study.vo.LoginUserInfo;
import com.study.vo.UsernameAndPassword;
import lombok.extern.slf4j.Slf4j;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.GlobalFilter;
import org.springframework.core.Ordered;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.core.io.buffer.DataBufferUtils;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.http.server.reactive.ServerHttpResponse;
import org.springframework.stereotype.Component;
import org.springframework.web.client.RestTemplate;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

import java.nio.CharBuffer;
import java.nio.charset.StandardCharsets;
import java.util.concurrent.atomic.AtomicReference;

/**
 * 全局登录鉴权过滤器
 */
@Slf4j
@Component
public class GlobalLoginOrRegisterFilter implements GlobalFilter, Ordered {

    //注册中心客户端 可以从注册中心获取服务实例的信息
    private LoadBalancerClient loadBalancerClient;
    private RestTemplate restTemplate;

    public GlobalLoginOrRegisterFilter(LoadBalancerClient loadBalancerClient, RestTemplate restTemplate) {
        this.loadBalancerClient = loadBalancerClient;
        this.restTemplate = restTemplate;
    }

    /**
     * 登录、注册、鉴权
     * 1. 如果是登录或者注册、则是去授权中心拿到token 并返回给客户端
     * 2. 如果是访问其他的服务、则鉴权、没有权限返回 401
     *
     * @param exchange
     * @param chain
     * @return
     */
    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {

        ServerHttpRequest request = exchange.getRequest();
        ServerHttpResponse response = exchange.getResponse();

        //1.如果是登录
        if (request.getURI().getPath().contains(GatewayConstant.LOGIN_URI)) {
            //授权中心拿token
            String token = getTokenFromAuthorityCenter(request, GatewayConstant.AUTHORITY_CENTER_TOKEN_URL_FORMAT);

            //header 中不能设置null
            response.getHeaders().add(CommonConstant.JWT_USER_INFO_KEY,
                    null == token ? "null" : token);

            response.setStatusCode(HttpStatus.OK);
            return response.setComplete();
        }

        //2.如果是注册
        if (request.getURI().getPath().contains(GatewayConstant.REGISTER_URI)) {
            //授权中心拿token : 先创建用户 再返回 token
            String token = getTokenFromAuthorityCenter(request,
                    GatewayConstant.AUTHORITY_CENTER_REGISTER_URL_FORMAT);

            response.getHeaders().add(
                    CommonConstant.JWT_USER_INFO_KEY,
                    null == token ? "null" : token);
            response.setStatusCode(HttpStatus.OK);
            return response.setComplete();
        }

        //3.如果是去访问其他的服务、则鉴权、校验是否能够从 token 中解析出用户信息
        HttpHeaders headers = request.getHeaders();
        String token = headers.getFirst(CommonConstant.JWT_USER_INFO_KEY);

        LoginUserInfo loginUserInfo = null;

        try {
            loginUserInfo = TokenParseUtil.parseUserInfoFromToken(token);
        } catch (Exception e) {
            log.error("解析用户信息token错误：【{}】",e.getMessage(),e);
        }

        //获取不到登录用户信息 401
        if(null == loginUserInfo){
            response.setStatusCode(HttpStatus.UNAUTHORIZED);
            return response.setComplete();
        }
        //解析通过 则放行
        return chain.filter(exchange);
    }

    @Override
    public int getOrder() {
        //值越大、优先级越小
        return HIGHEST_PRECEDENCE + 2;
    }

    /***
     *从授权中心获取token
     */
    private String getTokenFromAuthorityCenter(ServerHttpRequest request,
                                               String uriFormat) {
        ServiceInstance serviceInstance = loadBalancerClient.choose(
                CommonConstant.AUTHORITY_CENTER_SERVICE_ID
        );

        String requestUrl = String.format(uriFormat, serviceInstance.getHost(),
                serviceInstance.getPort());
        UsernameAndPassword requestBoy = JSON.parseObject(
                parseBodyFromRequest(request), UsernameAndPassword.class
        );

        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);
        JwtToken token = restTemplate.postForObject(
                requestUrl,
                new HttpEntity<>(JSON.toJSONString(requestBoy), headers),
                JwtToken.class
        );

        if (null != token) {
            return token.getToken();
        }
        return null;
    }


    /***
     * 从post 请求中获取到请求数据
     * @param request
     * @return
     */
    private String parseBodyFromRequest(ServerHttpRequest request) {

        //获取请求体
        Flux<DataBuffer> body = request.getBody();

        AtomicReference<String> bodyRef = new AtomicReference<>();

        //订阅缓冲区去消费请求体中的数据
        body.subscribe(buffer -> {
            CharBuffer charBuffer = StandardCharsets.UTF_8.decode(buffer.asByteBuffer());
            //释放掉 否则内存泄漏
            DataBufferUtils.retain(buffer);
            bodyRef.set(charBuffer.toString());
        });

        //获取request body
        return bodyRef.get();
    }
}
